In many industries, including, for example, the food and beverage processing industry, containers and other articles are transported from one location to another location by conveyors such as belt conveyors. In many such conveyor systems, a lubricating composition is used on the conveyor. One of the reasons that a lubricating composition is used is to facilitate movement and reduce the damage to the container resulting from mechanical impact between the containers and the rubbing action among the containers and between the containers and the belt. For example, occasionally in such systems, the containers are stopped on the conveyor due to a back up on the conveyor. While the containers are stopped, the belt is often still moved continuously. To facilitate the smooth transportation of the containers, a lubricating composition can be applied onto the surface of the conveyor belt and/or the containers.
There can be numerous challenges in providing lubricating compositions for use on conveyors. One example of a potential challenge is the variety of materials the lubricant may contact. For example, conveyors can be made of plastic, metal, or other materials, and the articles and containers being transported can likewise be made of a broad variety of materials, for example plastic, metal, glass, cardboard, paper, and the like. It is desirable that a lubricant be useful in more than just one application with one type of container and/or conveyor material.
Another potential challenge is the detrimental effects a lubricant may cause on the conveyors or on the articles and/or containers being conveyed. For instance, in some applications, the containers, or portions of the conveyors are made of thermoplastic materials. In such applications, it is desirable that the lubricating composition used be thermoplastic compatible. For example, in some applications that use fatty acids to make fatty acid soaps for use in lubricants, a high level of alkali neutralizing agent is required in order to neutralize the fatty acid in an aqueous composition. The use of higher amounts of alkali neutralizing agent, such as hydroxides and certain amines, in fatty acid soap containing lubricants, significantly increases the alkalinity of the lubricants. The increased level of alkalinity contributes to and promotes stress cracking in some thermoplastic containers, for example PET containers. The increased level of alkalinity can also contribute to and promote removal of some printed materials, such as printed codes on containers. Therefore, it is desirable that a lubricant not cause detrimental effects on the conveyors or the articles or containers.
There is also a desire for a lubricant with decreased pH sensitivity. Fatty acid based lubricants typically display decreased lubricity at low pH. This phenomenon is especially a problem in the beverage processing industry. For example, many beverages including colas, lemonades, and iced teas, have a low pH as a result of being acidic. Those commercial beverages having a pH slightly above 3 include COCA-COLA®, PEPSI-COLA®, ORANGE SLICE®, MOUNTAIN DEW®, SPRITE®, and MELLOW YELLOW®. Some are even more acidic with a pH below 3 such as MINUTE MAID LEMONADE®, MINUTE MAID ORANGE SODA®, FRUIT WORKS PINK LEMONADE®, and BRISK LEMON ICED TEA®. When acidic beverages are moved along a conveyor, they can spill and come into contact with the lubricant on the conveyor and lower the pH of the lubricant. This decrease in pH may decrease the lubricity of the lubricant. Thus it is desirable that a lubricant have decreased pH sensitivity especially in the presence of acidic beverages.
It is also desirable that conveyor lubricants that can potentially come into direct, indirect, or incidental contact with food and beverages for human consumption be composed of food additives or ingredients that can safely be consumed by humans or mammals. When a container for food or beverage is moved along a conveyor, the container touches the lubricant. The lubricant may not be rinsed off of the container before the container reaches the consumer. Consequently, there may be lubricant residue present on the container when the food or beverage is consumed. It is advantageous to have a lubricant that can safely be consumed by humans or mammals.